1. Field of the Invention
The present invention relates generally to pulse generators and more particularly to a novel technique for generating a periodic digital waveform composed of accurately timed pulse groups.
2. Description of the Prior Art
In the electronics industry of today, pulse signal generators are indispensible test instruments used in many manufacturing and engineering applications. They are commercially available from many different sources although not always under the same generic name. Sometimes they are refer red to as digital waveform generators, digital synthesizers, or pulse generators. Although commercial generators vary somewhat in the features offered, most models have the capability of producing pulse waveforms of variable pulse width (PW) and variable pulse repetition interval (PRI), and most have an accuracy to.+-.a few percent.
In the copending application Ser. No. 228,159 entitled "A DIGITAL PULSE GENERATOR HAVING A PROGRAMMABLE PULSE WIDTH AND A PULSE REPETITION INTERVAL" filed Aug. 4, 1988, which is incorporated herein by reference. a unique pulse generator is disclosed having capabilities beyond what is currently commercially available. One of the unique features of this generator is its ability to lock either the pulse width or the pulse repetition interval (or both) of the output pulse train to a precise reference oscillator preferably crystal controlled. In addition the generated pulses can be precisely set to almost any desired pulse width and any pulse repetition interval. Such a test waveform would be very useful in calibrating test instruments designed to measure such aspects of a repetitive digital signal. Unfortunately this generator can only produce single repetitive pulse signals, and there are instances where multiple pulse groupings are desirable. For example, in the design of radar receivers very precise adjustable pulse groupings are needed for test purposes.
An object of this invention is the provision of a pulse waveform generator capable of producing pulse groups having an adjustable pulse group repetition interval and adjustable pulse widths.
Another object of this invention is the provision of a pulse waveform generator capable of producing pulse groups whose time base is locked to a highly stable clock signal, such as a crystal controlled oscillator.
Still another object of this invention is the provision of a pulse waveform generator capable of producing groups of pulses having pulse repetition intervals and pulse widths which are independently programmable over a very wide range of values to an accuracy determined only by the time base accuracy of a reference clock signal.